Wrist-worn devices are typically secured to the person's wrist by means of a strap and clasp. When the clasp is in an unclosed state, the strap is open and/or sufficiently large or deformable such that it can be made to extend over a user's hand onto a user's wrist. A clasp is then used to limit the slack of the strap or to prevent deformation of the strap, thereby preventing the strap from passing back over the user's hand and thereby being removed. The wrist-worn device can be removed from the user by operating the clasp (by releasing it), thereby opening the strap and/or restoring the slack or deformable capability of the strap and once again allowing the strap of the wrist-worn device to pass over the user's hand. It may be desirable to determine when such a clasp has been released, indicating that the wrist-worn device has been or is about to be removed. Attempts to detect such clasp releases by means of measuring a conductivity or resistivity of the clasp or strap can be frustrated by environmental conditions, such as precipitation, and may also be deliberately overcome by, for example, shorting the detection circuitry. Degradation of the clasp or strap may also yield such measurements useless. For example, a degraded strap may never register as being closed or secure. Furthermore, it may be necessary to make the clasp or strap out of particular materials or to use a very precise (and therefore expensive) manufacturing processes in order to make the clasp and or strap suitable for use with these techniques.
A variety of clasp mechanisms are well known in the prior art. Typically, these mechanisms involve a trade-off between security and usability. For example, if the clasp is easy to operate then there is a risk that the clasp will accidentally be released while the wrist-worn device is being worn by a user, causing it to fall off. Conversely, if the clasp is more difficult to operate then it will be more secure. However, the clasp may be more time consuming or frustrating for a user to release when the user actively wishes to remove the wrist-worn device.